The present invention relates to open-end spinning and in particular concerns the starting up or resumption of open-end spinning, in which a ring of singularized fibres is placed in the groove of a rotor which turns at extremely high speeds, in which an end of the thread is re-introduced which connects with the singularized fibres placed in the groove.
By extracting the end thus introduced, production of the thread, which is twisted by the rotation of the rotor, is resumed. The thread is extracted by extraction rollers and wound onto reels.
The number of twists imparted to the thread is proportional to the ratio between the speed of the rotor and the thread extraction speed.
In an open-end spinning machine the thread must be rejoined in the starting stage of the spinning machine or, more frequently, when a thread has broken or when production of a new reel is started, having completed the previous reel. In order to perform this operation correctly the end must be reintroduced into the rotor using devices that ensure that a precisely-set length of thread is inserted into the rotor, with controlled times and speeds of the various organs involved.
To produce a good-quality yarn, in the section of thread produced in the joining operation between the end introduced and fibres taken from the rotor, the yarn must not be irregular, must not have a different diameter and must have the same resistance. In other words, in good-quality yarns the sections in which the join has been made must be the same as the rest of the yarn.
If this were not so, the yarn produced would have to undergo an additional spooling operation, to eliminate the imperfections due to irregularities of the diameter or twists, weak points and so on.
To obtain a proper join between the singularized fibres and the end of the thread reintroduced into the rotor with an opposite motion to that of extraction it is known from the state of the art that the said end must be properly prepared, ridding it of existing twists and making the fibres that comprise it essentially parallel, in order to improve the penetration between the fibres of the reintroduced end and the singularized fibres placed in the rotor.
In the known state of the art many devices for preparing the end of the thread are described, for example in UK Patent No. 1480399, U.S. Pat. No. 3925975, German Patents Nos. 2350842 and 2350843 in the name of Stahlecker or in Application for U.S. Pat. No. 659,040 in the U.S.A.
In spinning machines of more recent design, along the thread path between the exit from the rotor and the reel onto which the thread is wound there is a slub-catcher which checks for irregularities in the thread produced and interrupts the latter when it detects an irregularity in the thread which exceeds its calibration values. This improvement enables a better-quality yarn to be produced as compared to conventional spinning machines.
There are thus three types of event which require the thread to be rejoined:
- when the thread is no longer produced in the rotor, for example due to the supply of roving running out or to irregularities or dirt in the spinning rotor; PA0 - when the slub-catcher has come into operation, breaking off the thread; PA0 - when the reel is completed and replaced by a new bobbin (removal cycle).
In all these cases a rejoining cycle is performed which essentially involves cleaning the rotor, preparing the roving, picking up and preparing the skein end of the thread on the reel side, restarting the rotor and resuming the supply, reintroducing into it the prepared skein end, reextracting the skein end joined to the newly-produced thread and resuming winding of the thread.
In the first two cases the skein end of the thread must be found and picked up on the still incomplete reel in production, whereas in the case of removing the completed reel which is replaced with a new bobbin there are two possibilities: either the new bobbin is mounted with thread already wound on--in which case the previous case applies--or the new bobbin is empty, mounted in position and then wound with initial coils of yarn picked up from an auxiliary reel on board the service trolley (as in U.S. Pat. No. 4539803 of Savio) or from the reel just completed. After this initial winding the procedure is as described for the previous cases.
The present invention relates to finding and picking up the skein end from the reel side and its delivery to the organs that prepare the skein end to perform the successive stages of the rejoining cycle. Finding and picking up the skein end on the reel is generally done by using a suction nozzle which explores a generator of the reel and by making the reel counter-rotate to yield up the wound thread to the said inlet.
After picking up the thread, the nozzle draws back and delivers it to the organs that perform the rejoining operations. This pickup operation is not always immediately successful, since the thread may offer resistance to unwinding itself properly and entering the nozzle, causing the subsequent operations, which are performed "blind", to fail.
According to German Application for Patent No. 3225375 of Schlafhorst, this problem in spoolers can be overcome by fitting the nozzle with a sensor which signals when the thread has been picked up, subordinating the successive stages to enablement by this sensor. If the sensor signals that the thread has not been picked up, the skein end search and pickup operation is repeated, without proceeding to the next stages of the thread joining cycle--which essentially comprises rejoining the two skein ends, one from the reel side, the other from the spool side--which would constitute a waste of time and therefore use factor of the machine. This measure, however, does not disclose either the position of the skein end on the edge of the nozzle and thus its correct delivery to the joining organs, or how much thread has been taken from the reel.